


No King of Mine

by Draconicmaw



Category: Yu-Gi-Oh! Duel Monsters (Anime & Manga)
Genre: Besties in denial, Enemies to Friends, Gen, Kaiba finally has a body large enough to contain his ego, Merman Atem, Platonic Relationships, Platonic prideshipping, Sea-serpent Seto, TsundereExtraordinaire!Seto Kaiba, very much background vaseshipping
Language: English
Status: Completed
Published: 2019-10-27
Updated: 2019-10-27
Packaged: 2021-01-04 16:57:33
Rating: Teen And Up Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 5,680
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/21201020
Author URL: https://archiveofourown.org/users/Draconicmaw/pseuds/Draconicmaw
Summary: “Stay away from the trenches,” the elders had always said, so solemn and wide-eyed with fear, fear of the unknown, of the toothed beasts lurking in the absolute black, illuminated only the haunting, flickering lights of bioluminescent fish.Atem had always listened with rounded magenta eyes, imagined the gnarly maws and snapping jaws upon little mer tails. Mana listened intently, devoured the foreboding words with exuberance unrivaled.She knew Atem may be afraid -- and rightly so, if the elders were to be believed -- but she knew the young prince would never back down from a direct challenge.





	No King of Mine

**Author's Note:**

> Oooops, Draconicmaw writes another oneshot instead of working on her multi-chapter stories like she shooould be doing!  
Platonic!Prideshipping, where mer!Atem and sea-serpent!Seto are besties in denial. (Because everyone enjoys a good mermaid fic) Enjoy!

“Stay away from the trenches,” the elders had always said, so solemn and wide-eyed with fear, fear of the unknown, of the toothed beasts lurking in the absolute black, illuminated only the haunting, flickering lights of bioluminescent fish.

Atem had always listened with rounded magenta eyes, imagined the gnarly maws and snapping jaws upon little mer tails. Mana listened intently, devoured the foreboding words with exuberance unrivaled.

She knew Atem may be afraid -- and rightly so, if the elders were to be believed -- but she knew the young prince would never back down from a direct challenge.

“What a flounder!” she pouted when he once again vehemently protested a furtive journey to the trench. 

“I am  _ not  _ a flounder,” Atem replied, arms crossed. “I’m just reasonable.”

“ _ No, _ you’re just a wimpy flounder!”

His dark brows ticked hard, his ornate cranial fins flaring and his fluke lashing. Indignant.

Indignant Atem stopped at nothing.

Mana just barely kept her wicked, mischievous grin to herself. “The  _ only  _ way that I’ll believe that you’re not a flounder is if you go to the trench… all by yourself!”

Atem huffed, but those red-violet eyes were resolute.

And that’s how the story started.

* * *

Yes, here, the blackness was near absolute, the water freezing. The sheer pressure was the only thing keeping it from crystalizing into ice.

Atem shivered. From the cold, from his building dread.

He could die down here. A sperm whale could snatch him up, mistake him for a squid, or a giant squid itself might decide that a little mer prince would make the perfect snack at this time of day.

But, he supposed, the beauty made up for the foreboding darkness.

All around, bioluminescent bacteria and fish and jellies flashed their colorful lights, like the twinkling of stars in the clear night sky. They danced and drifted on the gentle current, and Atem paused a moment to take in the wondrous display playing out before him, his lips parted with awe.

A shocking blue flashed to his right. Rounded lights sparked in series, reminded him of the lightning that streaked the sky during harsh storms. Atem’s fluke curled with delight, and he admired the beauty of the moment.

The lights seemed to be getting bigger. Atem tilted his head.

No, closer. 

Then he realized that two of the lights weren’t flashing at all.

They were slitted eyes.

Surging toward him.

He gasped. 

The force of the blow pushed him through the water. A long, smooth, muscular body wrapped around him, constricted him, and Atem thrashed, caught a slippery neck in his clawed hand before jagged teeth could manage to sink into his throat.

Those slitted blue eyes burned brightly in the never-ending blackness.

Atem hissed, fangs bared, held those snapping jaws away even as the serpentine body began to  _ squeeze _ . Atem dragged his talons across the smooth, slippery flesh. The smell of blood stained the water, and the beast shrieked, darting away, nodes strobing in distress. Shaken, breathless, Atem reeled away, up, to the surface, before any more of those monsters came to aid their injured kin. 

Never again, he vowed. He would never come to the trench ever again. 

* * *

“Never again” came sooner than Atem would ever like to admit.

When he curled up amongst the corals at night, he dreamt of the lights. Of how they danced in their never-ending rhapsody. Like dust motes floating and twinkling little stars. Yes, Atem dreamed of swimming amongst those stars, as if he could swim through the night itself.

He had to see it again.

So, he swam down there with more caution than ever (not that he thought that possible).

He looked about himself constantly, watched for that string of flashing lights, for those slitted eyes. 

When he did spot them again, far into the distance, he distanced himself. But they were persistent, and Atem feared straying too far, of getting lost in this infinite abyss.

But they approached slowly, with just as much caution, and the light pulsated languidly.

Blue eyes stared, unblinking. “You…” a voice hissed, and the water rippled with the force of it.

Atem gulped. “Yes.”

“I’m supposing that you didn’t learn your lesson.” The lights pulsed in quick succession, a threat, before continuing their languid pace.

“I learned…” Atem replied, turned with gentle passes of his hands and twitches of his pelvic fins so he could watch those eyes circle him. “But I wished to see this place again. Your home is beautiful.” And dangerous.

Because, here, in the ocean, all things of beauty were things of unbelievable danger.

Like the pale blue lights of the serpent before him. 

“Hn,” was its only reply.

Atem turned again. The creature was circling him, studying him, and the young mer prince made sure to stay on guard. 

He could only imagine the damage those jagged teeth could do.

“You’re small for a serpent, according to the tales I’ve heard,” Atem mentioned, thoughtless of the consequences that insulting this beast could entail.

A chuckle, purring and sibilant. “I’m young. I have a lot of growing to do. Trust me, in two decades time, I’ll be large enough to squeeze the life from the largest of whales.”

Atem snorted. “I believe it.” Though it did sound like wishful thinking.

Or maybe Atem was biased; he was tired of being the small one.

“What’s your name, serpent?”

A beat of silence, save for the rippling of that long body through the frigid currents. “Seto.”

Atem tilted his head. “Greetings, Seto, Serpent of the Deep. I am Atem, Crowned Prince of the Mer.”

A rattle, like teeth clacking together repeatedly. “Your title means nothing here, little fish. I care not for your silly monarchy.”

Atem bristled. “Silly? I will have great power, you realize.”

“Will you now?” Yes, those unblinking blue eyes were  _ smirking _ . “It won’t affect me any. Silly, silly mer.”

“Hmph. Well, just know that if you kill me, an entire kingdom will hunt for your head,” Atem crossed his arms, frowned at the beast circling him.

“As if all your shrimpy soldiers are brave enough to come this deep to find me. After all,  _ you _ may be brave, but you’re clearly an idiot.”

“An idiot that bested you in battle,” Atem pointed out, bristling with challenged pride.

“Just you wait,” Seto hissed. His nodes flashed with irritation. “When I’m bigger, I’ll kill you without a problem.”

“I’m looking forward to it.”

* * *

Seto did grow, but so did Atem, and what Atem lacked in size, he made up for with speed, agility, and ingenuity. 

After all, Atem would jibe, it must be difficult to maneuver with an ego of that size.

Their marine chases unraveled through the glowing depths, up, around the black-shrouded rocks of the shallower (but still abyssal) waters, and, under the cover of night, amongst the coral on the continental shelf.

Seto, Atem discovered, was pure white, and he rippled through the water like the human silk Atem had seen in a sunken ship. He’d never seen a sight so haunting, or so beautiful.

Both exhausted from their strenuous… fighting (playtime), they would settle on the sand, and, what started as silence, became long conversations, sometimes as competitive as their chases, sometimes inane, sometimes inquisitive as they questioned the watery world in which they lived. 

Days became months, became years.

Never once did Seto manage to kill Atem.

* * *

After Atem’s father died and he took the throne, he had much less leisure time. Problems and crises bled into one another, formed one huge headache that consumed much of Atem’s life for the next decade.

His father’s reign had been a poor one; the scars of genocide left the people in a perpetual state of political unrest, and insurgent forces rose against the new king by the day. But still, no matter how little he could, Atem managed to find time to spar with the Serpent of the Deep.

Even as he swam into Seto’s territory, Atem remained on his guard. Mer insurgents were killing any of Atem’s men that they could find, and the sea serpents were known to be covetous; battles for territory were violent and bloody.

And it wouldn’t have been the first time Atem had swam right into Seto viciously fending off an invader.

But all was still, all was silent. 

Glowing creatures drifted on the current like cosmic beings given flesh, but, most of all, he swam towards the huge, pulsing lights.

Seto had told no lies; he was gargantuan now -- with his sheer size alone, he could crush the entire mer capital. Those nodes that had captivated Atem so long ago pulsed like blue miniature suns in the ocean’s black depths. Seto illuminated all around him in a splendid display of vitality and majesty. The eerie glow of his immense blue eyes caste harsh shadows on his jagged fangs and haunting face. 

\-- Atem could easily swim down his throat, Atem thought with errant humor --

“You again,” Seto breathed, and his voice throbbed so deeply it became the current itself. His coils flexed and shifted amongst the ship graveyard that had become his hoard and den.

“Yes, it is I, my old enemy,” Atem echoed with no small amount of wry humor. He spread his arms, lit by Seto’s endless glow. “You’re looking awful as ever, Seto.”

“Seto Kaiba,” the serpent corrected, tongue flicking out a moment, pupils contracting into harsh slits.

Atem paused in confusion.

“I have earned another title,” Seto Kaiba hissed, “One worthy of display.”

Amongst the serpents, one keeps what one kills.

“Ah,” Atem replied. Seto often bragged of his kills, but never had he been proud enough to take on the name of his fallen enemy. 

“What brings you here, little fish?” Seto Kaiba murmured, and his nodes pulsed in succession, a blinding display from one so large.

“I’ve come to spar again, old enemy.”

“As if you could hope to defeat me,” Seto Kaiba replied, and, all around, metal and wood creaked with the tightening of serpentine coils. 

“As if you could hope to maneuver properly to catch me,” Atem smirked, flicked his tail dramatically, twirled in the water gracefully. “Perhaps you should lighten up on the whales. All of that blubber is going straight to your ribs.”

Those huge, unblinking eyes motionlessly watched each energetic loop and spin, save for perhaps the slight contraction of black, slitted pupils. “I didn’t realize that the King of the Mer would stoop to petty insults.”

Atem scoffed challengingly. “Like I could resist when Seto Kaiba of the Deep is looking plump as a manatee.”

That huge head reared back, aural fins flaring, nodes flashing threateningly, and Seto was lunging. 

Atem laughed, and those deadly jaws missed him by a long shot; one powerful pump of his fluke had him zooming away.

“I’d eat you this instant, if I didn’t think you would taste like rotting shark, little fish,” Seto Kaiba rumbled.

“Ah, but we’ve already established that, with your sheer obesity, you could not catch me even in your wildest dreams.” 

Though serpents rarely slept, and dreamed even less.

With each mighty lunge, wholly playful despite those flaring lights, Atem ducked away, and the sheer  _ current _ of Seto moving his head back into its original position sucked Atem closer.

Before he departed, he playfully patted a gargantuan white flank. Seto Kaiba rumbled threateningly, but allowed his oldest enemy to swim away unscathed. 

Seto Kaiba settled back, a huge pale, glowing beacon in the cosmic sea, and stared into the darkness.

* * *

It was only a matter of time before it would have happened, but even in their worst nightmares, Atem and his royal advisors hadn’t imagined it would be so soon.

The insurgents had recruited the help of another mer kingdom. Of course, they would be foaming at the jaws for a chance to invade and take over.

Atem lacked the men, the power to hold off an invasion from such a formidable force.

“We have one last hope,” Atem announced to the court.

Mahad, Atem’s right-hand-man, flared his cranial fins in interest and fear. “And what would that be?”

Atem smiled wryly. “I must request aid from an old enemy.”

The court erupted; the current itself shifted with the force of their sound. Their king had an enemy? One that they weren’t currently contending with?

“I will depart for the trench before the sea eats the sun,” Atem declared, but his words only stirred more dissent.

“My king!” Mahad cried. “What is this madness?! The trench is no place for you to be! The risk is far too great in this tumultuous time.”

Atem shook his head. “You cannot stop me; I forbid it, though you are more than welcome to accompany me to the Deep.”

* * *

Mahad glanced about nervously. He and his king were loosely tied together by a line of kelp as the other led him deeper into the dark. It wasn’t long before they were seeing the glowing specks, the dancing lights of the near-blind creatures that managed to eek out a living in the desolate black. 

“My king…” Mahad murmured, tense. In the faint glow, his poorly-adjusted eyes could just barely make out Atem’s silhouette; even so, he could see distinctly his king’s utter ease.

“Fear not,” Atem said. 

What Mahad thought were close, small lights pulsing in this cold abyss were actually  _ very large _ lights pulsing  _ very far away _ .

He froze, but Atem, with a powerful pump of his tail, managed to drag his advisor and bodyguard along. 

From the dark, a pale shape coalesced under that eerie illumination. Coils, leagues of them, flashing and shifting amongst a desert of sunken human ships and the skeletal remains of serpents and cetacean alike. And two huge, slitted orbs of blue light.

Eyes.

They cast haunting light on a harsh face and monstrous teeth.

A sea serpent. The size of which Mahad could never fathom.

They stared unblinking at the two comparably tiny intruders. Mahad looked frantically to Atem, whose solemn face was easily irradiated by those titanic, glowing irises. 

“You again,” the beast rumbled, and the vibrations of its voice alone almost sent them drifting back.

“Yes, it is I, old enemy,” Atem replied calmly. “You’re looking awful as ever, Seto Kaiba.”

A hum… almost…  _ humorous _ .

_ Seto Kaiba _ stared at them, more specifically at Mahad, though with the sheer size of those eyes, it didn’t have to move its head at all to focus on the foreign mer.

“You brought a companion. Good. You alone would hardly sate my hunger,” Seto Kaiba hissed, jaws parting and closing, like a giant trap of glass needles. 

Mahad froze, but Atem was relaxed as ever. “My king…” Mahad frantically whispered.

Atem waved a hand dismissively before he was regarding the giant of the Deep once again. His magenta eyes were washed violet by that pale blue light. “He would not allow me to travel here alone, as I forbade him from barring my journey. Seto Kaiba, this is my royal advisor, Mahad.”

Unblinking stare.

“Mahad, this is Seto Kaiba, Serpent of the Deep, Hoarder of Ships, Slayer of Kin, Collector of Blubber.”

Mahad stared, stunned, as Atem smirked on the last phrase.

A rumbling growl. Fins flared and nodes flashed in a blinding display. “You best not anger me, little fish.”

Atem nodded, crossed his arms, and his expression once more became that of a solemn king. “Indeed, for I must request your aid, old enemy.”

Seto Kaiba shifted, his coils squeezing momentarily around the ships in his hoard. “My aid? And why would I aid you, the thorn in my side since long ago?”

“I’m sure you have heard; insurgents threaten to topple my kingdom, and they gained favor from another mer nation. It is only a matter of time before I, my court, and my people fall. You are my last resort, old enemy. Know it is with despair that I come to you now.”

The huge serpent remained silent. It was hard to tell if he was being thoughtful; his expression never changed, eyes never blinked, only cast that eerie blue light perpetually. Then, finally, it replied. “And what would I gain if I helped you?”

“The ever-lasting devotion of my kingdom. If you wished for something we could provide, we would do so without hesitation or question.”

Mahad whipped his head over to Atem, his eyes wide.

But Seto Kaiba hummed, and  _ yes _ , it was laughter. Mocking and derisive. “What would I possibly want from you? What a pathetic offer.”

Mahad bristled. “You dare disrespect the king--”

“He’s no king of mine,” Seto Kaiba interrupted, voice raised barely louder than normal, but it was enough to boom through the cold abyss.

“I respect that,” Atem replied. “Though I never would have thought you would so readily allow another to defeat me.” The words were decidedly dismissive, and Atem crossed his arms. “I suppose our bonds as eternal enemies mean nothing to you.”

Seto Kaiba arched up, rearing, towering high above them, slit pupils contracting until nearly pure discs of blue glared down upon them. “No one but I will have the pleasure of taking your life, Atem of the Mer.”

Mahad gripped Atem’s shoulder. But the muscle and bone were relaxed.

“Then you may want to defend your claims to my death. An encroacher is more than willing to do it for you. He will steal the glory of ending my life from you if you remain complacent.”

And Mahad finally came to terms with what Atem was doing.

There were two things that drove serpents: their pride and their possessiveness.

“As if I would let him!”

* * *

The mer hovered, staring overhead with fear and awe.

The figure was so large it blocked out the light of the moon, but the strobing blue nodes along its sides replaced it in a spectacular display. 

They would have darted away in sheer terror had they not seen their king swimming languidly alongside the titanic serpent. He looked miniscule next to the enormous beast. 

"By Tethys," someone breathed. "Look at the size of that thing."

"Is this what our king meant… an old enemy?"

That massive body coiled about. The huge, pale segments of its body cautiously settled down, careful of the numerous coral and stone buildings. It had enough length to circle once about the capital and then some. It lifted its head, fins flaring, unblinking eyes staring into the depths. 

The water vibrated. Loose objects rattled on their shelves.

It was  _ singing _ . The beast was singing. The notes themselves were either too deep or too high for the mer to hear, but they could  _ feel _ the melody deep in their bones. 

The singing continued for all hours, until, the next night, two other massive shadows fell over the capital.

A black serpent, smaller than the first but still so incredibly gigantic, with pale purple nodes that pulsed excitedly at the sight of the beast coiled about the city. 

And another white one, perhaps more silverish. It had no nodes, but bright blue eyes still glowed down upon the city. A female, and she was even larger than the first. 

The first had summoned his family. 

It was not common amongst serpents, but some had tight familial bonds, and they formed pods that would reconvene every couple of years to catch up and enjoy one another's company. 

The mer shivered in awe. They had underestimated the greatness of their king, Atem, who, seemingly without effort, summoned to his aid three of the most powerful beings to ever swim in the ocean. 

* * *

Even Atem was stunned. 

He looked at each of the three massive heads in turn.

Kisara Kaiba, the matriarch.

Seto Kaiba, the patriarch.

Mokuba Kaiba, the youngest.

"You…"

"With opposition such as this, they shall regret the day they were born, much less the day they decided they would invade," Seto Kaiba rumbled. 

"I have no doubt," Atem replied, breathless. "I… I cannot express my gratitude. It is truly fathomless."

"Save it for someone who cares," Seto Kaiba replied flippantly.

Atem could only shake his head and smile.

* * *

The insurgents were confident, loud, as they advanced upon the capital. They had numbers and resources unparalleled by the target in their sights. 

"What  _ is  _ that?" One soldier asked. It looked like a wall, tall and white, had been erected around the capital.

And then it pulsed, blue lights flashing. 

"It matters not! We will not let a few flashing lights keep us from victory, will we, men?!"

They cheered, the whole school of them pulsing with energy.

But then, the white wall moved. A massive head, unblinking blue eyes, raised up. Even from this far away, they could tell that the beast was huge enough to swallow them all in one gulp. 

"Holy shit."

Had they got the location wrong? Were they swimming right into a serpent's lair? Or had this beast conquered the capital before they'd had the chance to?

No. Right over the fins cresting its endless spine, a swarm of soldiers hovered in waiting.

"Poseidon's beard, they have a fucking serpent."

It was almost enough to cow them, but they were whipped up, frenzied from their victories further south, their appetites stirred by the scouting party they had slaughtered just that morning.

So they advanced. Then, they felt it. The water was vibrating. 

And then a shadow fell over them. 

From seemingly nowhere, a titanic sea serpent circled above. Pale like the other, but where the other had flashing nods, this one had huge flaring fins. She spread them out, and they billowed like sails. The membranes flushed with color in an intimidation display that was certainly effective. 

The vibrations grew in intensity.

And then they were bathing in purple light. 

An enormous black beast was flanking them. It's nodes pulsed and strobed with blinding frequency. 

They were surrounded by giants. 

The two swimming frighteningly close -- not close in actual distance, but the beasts moved enough water as they swam to make the currents churn. 

Even with reinforcements on the way, they would never hope to take the capital. 

"Fall back!" a general cried, and the school regrouped, preparing to come about and retreat, but when they turned…

A pitch black flank was barring the way. 

Crying out, shouting, confused, they looked about.

With stealth impossible for such immense creatures, the two had closed in. The black one, smaller, was twining around them in tightening horizontal loops. It was corralling them in with its body. 

"Ascend! Ascend!"

So they darted up, hoping to escape the writhing column of strobing sea serpent.

But there she was, the massive female, curling herself into a vertical ring around the smaller male. The tops and bottoms of the column were now sealed up by colorful, flaring fins. Though, at the top, was also her terrible maw to contend with. 

The vibrations were overwhelming. 

The beasts were singing, communicating with one another.

In the living prison they now found themselves trapped in was illuminated only by pulsing purple light and eerie blue eyes. 

An army of two thousand, subdued by two overgrown eels. 

A soldier, crying, panicked, terrified, surged forward, his spear readied. The sharpened obsidian tip merely glanced off the thick black hide. 

They lost the fight before it had even begun.

* * *

“By Tethys,” Atem breathed. He was clad in his battle regalia, the plating glimmering alongside his brilliant red tail. 

Seto Kaiba hummed, his gargantuan head hovering close by. 

“Though that is a sizable army, I doubt that is all of their troops,” Atem said. He turned to his colossal friend. “We will engage them. I am uncertain, even in this situation, if they will surrender easily.”

“Worry not. One wrong move and they’ll be devoured whole or crushed.”

Atem inclined his head. “I trust you will guard our city in case of reinforcements?”

“I’ll protect your pathetic sand castles, little fish.”

Atem tipped his head in a nod, his eyes genuine, and set a hand on Seto Kaiba’s snout before his fluke was pumping powerfully, propelling him to lead his soldiers forward. It was a bit of a swim to get out to where Mokuba and Kisara where containing the enemy forces.

Had they not the serpents’ aid, Atem knew his own men would’ve been inconsolable -- they did not have the numbers to fight off their enemies if they had reinforcements. But with the power of three nearly god-like beings on their side… it was safe to say that morale was high. 

“Extraordinary,” Mahad said quietly from his king’s side. Mokuba’s gray-purple eyes watched them approach, and he shifted, his coils parting just enough to let in Atem’s forces. 

Enemy soldiers were immediately surging upon Atem, when, suddenly, a monstrous sable head was ducking down, jaws parting -- fangs like glass needles -- and then snapping shut like a trap. Mokuba had just eaten two dozen enemy soldiers like a blue whale would gulp down krill.

“We do not want war!” Atem shouted over the panicked din that ensued. “That is why you are subdued, not devoured on sight!”

“How did they go down, Mokuba?” a sonorous, melodic voice asked from directly above. Kisara’s unnerving blue eyes were focused down on the swarm trapped beneath her.

“... Swimmingly…” he replied, jaws parting and closing, teeth clicking. 

The enemy troops were now frozen.

“You will come willingly…” Atem began, and then gestured to the massive coils about them. “Or face the consequences.”

* * *

Seto felt their vibrations on the current. Indeed, more were swimming that way. And it was a much larger force than the other one. He sang softly to his brother and sister. They would alert Atem. 

The enemy forces were drawing closer. Thousands of them. 

“Take cover,” he bellowed to the mer people in the city below. They scrambled to obey, and he shifted. His long spine began to undulate, off the sea floor, then back down, over and over, creating a massive wall of writhing flesh. It’d be much harder for the ones that managed to dart past his maw to actually penetrate the city. A clouds of silt billowed up, but not enough to totally obscure anyone’s line of sight.

The troops -- ones that Atem had ordered to remain behind in case of this very scenario -- readied their weapons. 

They emerged from the oceanic mountains, swarming over it like a school of mackerel. A rainbow of color, but a harbinger of war and death. Seto growled lowly, fins and crests flaring. The army paused upon seeing the immense pale beast in their path.

They were shifting there, just out of the hemisphere of Seto’s hearing, but he was sure they were plotting, regrouping. It was only the barest amount of time before they were surging forth once again.

They were hoping to overwhelm him with their sheer numbers. 

His nodes flashed, faster, brighter, and he exerted just enough energy. His flesh was vibrating with an electrical buzz. The water surrounding him crackled faintly. 

“Take cover!” he bellowed again, this time to Atem’s soldiers. They were quick to dart to safety. 

The electrical charge built, greater, greater, and it crackled at the back of his throat. His jaws parted. His neck arched, and the blast came forth with enough force to push his head back even further. Electricity was difficult to direct underwater -- the salt dissolved in the ocean could easily carry the charges away, but this bolt traveled clear and true, rushing through the depths, causing massive explosions on the way as the charge super-heated the water far past its natural boiling point. 

The effect was devastating, cleaving the enemy forces in two, and leaving many dead in its wake. The surrounding waters were now several degrees warmer, and the heat rose in mirage-like waves. 

Those in the capital’s towers who had bore witness to Seto’s incredible display stared in awe. 

“By Tethys.”

But the opposing forces continued with their headlong rush to their own demises. 

For now, Seto could only watch them approach. That big of a blast required quite the recovery time. 

But it was more than worth it. He’d taken out a third of the invading army and split the rest in two. 

He arched his neck, fully prepared to dive in and snap up as many as possible in his maw. 

But as the army approached, a huge current surged against them.

It was Mokuba, diving in. Such a massive creature moving so swiftly caused a lethal riptide that tore apart any that were unfortunate enough to get caught in it. Mokuba coiled back around, monstrous jaws gaping wide. 

Seto could hear the screams all the way from where he was still coiled about the city. He dared a quick look to where the first invading force had arrived. There was about half as many enemy soldiers -- either killed by Atem’s troops in self-defense or devoured by Kisara or Mokuba. 

She was following overhead, a foreboding shadow and deadly reminder that resistance was futile. 

He looked back over. Some were just close enough. Seto Kaiba surged forward, slithering from around the city in his charge. Just as swift as Mokuba, he was snapping up the little mer morsels in his colossal jaws. He barely felt them pass down his throat. 

“Fall back!” generals cried, but it was too late. A majority of their forces had been utterly decimated, and Atem’s troops were darting out to apprehend the stragglers. 

When night came, the capital stood, wholly unscathed.

* * *

The next day, there was a city-wide celebration in the serpents’ honor. Kisara and Mokuba only lingered for a little while before they were swimming off into the depths. They had territories to protect, and no doubt had squatters to fight off. 

“We wouldn’t have been able to do it without you, Seto Kaiba,” Atem said, close to his old enemy’s head, “You have my endless gratitude.”

“Your gratitude means little to me, little fish,” the serpent replied, though both knew that it was a lie, and both knew that the other knew as much. 

“Several of the architects already have plans for a temple in your honor, and many are petitioning to erect a statue dedicated to you in the entryway of the palace,” Atem informed him with a sly grin. 

“Finally, your people have found a decent deity to worship,” Seto rumbled, and Atem was sure that if he could have done it, Seto Kaiba would’ve rolled his eyes. “It’s about time lesser beings started bowing beneath my clout.”

“Ah, your ego is showing. Careful, it might end up crushing the city you were defending.” Atem nudged the massive snout with his elbow. “Several of our women are offering themselves up to be your wives.”

Seto Kaiba snorted. “What would I want with mer wives? Silly, the lot of them.” 

Atem shrugged. “The marriages would certainly be symbolic, but, perhaps they can tend to your temple and the innumerable gifts people are crafting for you?”

“How about I just don’t take your strange fish women for brides.”

“I doubt even you can dissuade them. Mer women are strangely stubborn that way.”

“Whatever. Do with them as you please.”

“Temple maids it is,” Atem said with a snort. “Sad that an overgrown, overweight eel has more women vying for him than this nation’s king.”

“True. Perhaps mer women have more sense than I previously assumed.” A humorous, derisive hum and a teasing clattering of fangs. “Do you not have a harem?”

“No. I have a single wife. She treats me well. I have no need for another.”

“Strange for your people, is it not?”

“Perhaps. I care not for normality. Millennia of tradition has simply steeped our society in stagnation.” The serpent only hummed, so Atem gave him a wry grin. “You know, it is because of my wife that we first met.”

“How so?”

“Of course, we were not married so young, but she was my closest childhood friend. She’d goaded me into venturing to the Deep on my own.”

“You are very easy to goad,” Seto Kaiba replied simply. 

“... No comment.”

A snorting chuckle. 

Atem leaned more of his weight onto Seto’s smooth snout, and the serpent simply let him. The pair watched the festivities from high above the capital.

“You’re lucky I’m not taking the chance to eat you right now.”

“What’s stopping you, then?’

“All those soldiers I ate yesterday have given me an upset stomach.”

“You poor thing. Whatever will my people do when their new deity has a belly ache?”

“... You’re in troubled waters, little fish.”

“I’m sure.”

* * *

The swim down was hard on his old bones. The cold made him ache, but he pushed through, continued to swim through the eerie speckled abyss. But that blue glow ahead made him smile faintly. The wrinkles on his face creased deeper, but, even in his old age, he was a regal king. 

A massive head turned, and those blue eyes fixated on the elderly mer that had swam into his domain.

“You again.”

A hoarse chuckle. His voice was wrought with age, yet it still held that youthful humor, the smug edge, the stately tone. “Yes, it is I, my old enemy.” Scarred, but still well-built arms crossed over a thinning chest. “You’re looking as awful as ever, Seto Kaiba.”

A hum, humorous. “Says the little fish who looks like he just swam out of the back end of a shark.”

“I’ve come to spar again.”

“As if you could hope to defeat.”

Not once did Seto Kaiba manage to kill Atem.

* * *

Scrolls upon scrolls were written about the pact that had saved their city, about the three monsters that had emerged from the Deep to keep the mer city safe. Atem was revered for his sway over the beasts. 

But few knew that it was not a pact that Atem had made with the gods, that he had not sold his soul to the serpent in return for a favor.

Few knew that it was simply because of the friendship between a little mer boy and a hatchling serpent. 

**Author's Note:**

> If you want to know what Seto and co. look like, imagine a viperfish and a moray eel had a giant bioluminescent lovechild. The females generally live in shallower waters (still pretty deep, but shallower in comparison to the trenches) where they lay the eggs and cover them with their fins until they are hatched, upon which they are fully developed and capable of hunting on their own like snakes. Very few survive until adulthood. All of the young have the bioluminescent nodes, which they use for hunting, but they become less useful for those purposes as they get older. So, adult males use them for intimidation and mating displays, and females lose them entirely, although they still have bioluminescent bacteria in their eyes.  
Anyway, Draconicmaw’s fictional creature zoology lesson is over! I hope you enjoyed the story! It was a lot of fun for me to write.


End file.
